A latex balloon, wall thickness 3.091 x 10-4 m, contains helium at a concentration of 0.3 kg m-3. Under these conditions the total surface area of the balloon is 0.33 m2. The diffusion coefficient of He in latex at room temperature is 4.9 x 10-9 m2s-1. Calculate the rate of helium effusion (in g/hr) from the balloon.